There are many situations in which pedestrians or vehicles may be carrying materials which are prohibited from transport into or out of a designated area, such as, airports, sporting venues and high security facilities. The prohibited materials may include, for example, explosive materials and illegal drugs.
One method for screening for such materials is to individually search each pedestrian or vehicle for the prohibited material. Unfortunately, individual searching is extremely time-consuming and requires an inordinate number of searchers and an inordinate period of time.
Another method for screening for certain materials includes the use of detection systems or devices and instrumentalities. Such systems typically use ion mobility spectrometry (IMS) and are designed to detect certain chemicals, more specifically, particular airborne particles associated with the item for which detection is intended. As described in further detail below these types of systems suffer from various problems and prove inefficient and/or ineffective when compared to canine/dog sniffing detection methods.
The use of dogs as chemical detectors dates back to their use as hunting dogs several thousands of years ago. More recently, however, e.g., since World War II, dog-handler teams have been used extensively by the military to locate explosives. Civilian use of dogs first started with tracking individuals and locating drugs and other illegal contraband, including bombs and other explosive devices. Civilian use has now expanded to include the detection of many other items, such as, guns, pipeline leaks, gold ore and contraband food. In view of recent terrorist activities dogs are now being trained to also detect flammable and ignitable liquid residues to identify individuals that likely have recently handled materials potentially used in bomb manufacture. Such canines are commonly referred to as accelerant detector dogs and results of their odor detection in such situations have been found admissible in court in certain circumstances.
A general comparison between instrumental chemical detection devices and trained detector dogs demonstrates that for certain aspects instrumental detection may be preferable over canine detection. However, for many, if not most, aspects that are most important to the user, canine detection is the more preferable choice. For example, the selectivity of detector dogs is generally superior to instrumental methods. Dogs are able to generalize odorant signatures enabling the detection of target odors in the presence of additional significant distracting odors, without the false alerts commonly encountered with many instruments. Dogs use a highly sophisticated neural network to confirm explosives from the pattern of odor chemicals emanating from their representative parent molecule(s) rather than relying on the parent molecule required by most instrumental methods.
Another advantage of detector dogs over instrument methods is the overall speed of detection which is generally significantly faster in canine detection than instrumental methods. The detection of low vapor pressure explosives using typical IMS instruments requires trapping particles containing the adsorbed explosive vapors followed by transferring the particles into the detector for heating and analysis. This additional required step slows down detection times for instrument from seconds to minutes or even longer depending on the screening and swab time as well as the number of subjects/items to be tested in a given period of time. Dogs also utilize an extremely efficient sampling system and can often times go directly to the source of the odor and discover the explosive, unlike machines which are typically fixed.
Even though canine detection is preferable over machine detection for many reasons, bringing certain dogs into direct contact with a large number of pedestrians, or even vehicles, can present difficulties. For instance, some people are extremely fearful of dogs and other animals and, as a result, a person being screened may act irrationally and cause harm to a highly trained dog or its handler if the situation is not tightly controlled. Traveling among a large number of vehicles may also create the potential for harm to a highly trained dog or its handler. What is needed, therefore, is an accurate and reliable system to screen persons or other individual items, such as packages, baggage and other items, and obtain consistent positive identification of prohibited material while reducing false-positive identifications of prohibited material.